Join works but we unable to join the row incrementally (we dont want to join unchanged row on each run).
Imagine to join incrementally row. For instance, userId=A lands into tableA and userId=B lands into tableB. The incremental join would result in:
1. row(userId=A, colA=1, colB=N/A)
2. row(userId=B, colA=N/A, colB=1)
For incremental update, we are thinking using MERGE INTO (partial update) into target table so we retain column value from other sources.
For your reference,